The present invention relates to a method for determining the activity of cholinesterases.
There are known two kinds of cholinesterase, namely, (1) true cholinesterase, and (2) pseudocholinesterase. True cholinesterase can be found in human red blood cells and human nerve tissues. Pseudocholinesterase can be found in human blood serum and in the human pancreas. Both kinds of cholinesterase decompose (hydrolyze) acylcholines (e.g., acetylcholine) to choline and an acid (e.g., choline and acetic acid). The present invention is effective for determining the activity of both kinds of cholinesterase. The term, cholinesterase, used hereinafter, includes both true and pseudocholinesterase.
When a person suffers from hepatic disease or anemia, the amount of cholinesterase in the blood decreases. When a person suffers from nephrosis, diabetes mellitus or a disease of the nervous system, the amount of cholinesterase in the blood increases. A diagnostic indication of the existence of the diseases mentioned above can be made by measuring the level of cholinesterase in the blood. The accurate determination of the activity of cholinesterase contained in the blood serum is therefore significant from physiological and clinical viewpoints. As conventional methods for making that determination, there are known (1) the Takahashi and Shibata method, in which acetyl choline is used as a substrate and the variation of the pH caused by decomposition thereof is measured, and (2) a method in which benzoylcholine is used as a substrate, choline liberated from the benzoylcholine is oxidized with choline oxidase to liberate hydrogen peroxide (H.sub.2 O.sub.2), the hydrogen peroxide is subjected to reaction with phenol and 4-aminoantipyrine with peroxidase to produce quinonimine dye, and the concentration of the quinonimine dye produced is colorimetrically measured.
However, such conventional methods have disadvantages. The method (1) requires complicated steps and the method (2) does not give good measurement results with high precision.
It is an object of the present invention to provide a simple method for determining the activity of cholinesterase.